1. Technical Field
This invention generally relates to hammers used in hammermill assemblies, and more particularly to a non-swinging hammer held in place by a pair of rods wherein the hammer body has an interlocking slot to receive one rod, and a rod hole through which a second rod is interfitted.
2. Background
Hammermills are used to grind a disparate and wide range of materials, including such things as tree stumps and slash from logging operations, land fill trash, to food products, such as grinding apples into mash in preparation for making apple cider. A typical hammermill assembly is formed of a rotor assembly to which a number of hammers are attached, a fixed cutter bar positioned alongside of the rotor assembly and in close relationship to where the hammers will pass by it, and beneath the rotor assembly a semi-circular screen. Material is dropped into the hammermill from the top, where it is impacted by the rotating hammers, and rotated around to a point where larger material will also impact the cutter bar and break, and then pass beneath the cutter bar into proximity to the screen. Depending upon the screen size, the smaller material will pass through the screen to a collection point beneath the hammer mill.
FIG. 1 discloses a portion of a typical prior art hammermill assembly in an exploded view. It shows the central rotor shaft, which, in the prior art, is typically a keyed shaft and a plurality of alternatingly arranged spacers and hammer rings. Hammer bodies are sized to interfit between the hammer rings and are provided with two rod holes. A plurality of hammer rods can then be inserted through aligned sets of rod holes in both the hammer rings and the hammer bodies to lock the hammers firmly in place. While there are other designs for hammermills which provide for swinging hammers which are held out in an extended position by centrifugal force, this design for a fixed hammer is quite common.
The problem is that the hammers undergo substantial wear and stress during operation. As a result, as shown in the prior art FIG. 1, there is often times a wear tip bolted to the tip of the hammer head to reduce wear. However, even with the wear tip, hammers do occasionally, and in some cases routinely, break, and therefore must be periodically replaced.
Hammermills used for many applications must be very stoutly built using high strength alloys of steel which must be machined to relatively close tolerances. As a result, when a hammer head breaks off, two sets of hammer rods must be unbolted from the hammer mill assembly and removed to release the broken hammer so that it can be replaced.
If the broken hammer resides in the middle of the hammermill assembly, this may result in the withdrawal of the hammer rods past many rings to get at the broken hammer, resulting in the removal and reinstallation of a number of hammers just to replace the broken interior hammer.
This is not always an easy thing to do. The hammer rod must be unscrewed or unfastened from the hammer rings. If any of the rings or the rod have deformed during operation, the rods may not be easy to remove. In fact, in a number of applications, for example that which is disclosed in the grinding apparatus shown in U.S. Pat. No. 4,997,135 to Zehr, special built-in hammer rod extractors or punches are provided to hydraulically push out the hammer rods so that broken or worn hammers may be repaired or replaced. Also, it should be apparent that in the prior art, in order to replace one hammer you have to push out and remove two hammer rods. Thus, all of the other hammers that precede the broken hammer must be also removed and then reinstalled. At best, this is a time consuming and difficult job.
Accordingly, what is needed is a hammer design for a fixed hammer, as opposed to a swinging hammer that can be removed by the removal of only one hammer rod, as opposed to two. The achievement of this object also achieves secondary objects, such as greatly simplifying the process of replacing broken or worn hammers, and greatly reducing the amount of time it takes to do so.